FlyRyde

yeah I'm gonna do that first. That's a free option, so why not? Maybe they were about 30, not 25 at first.

gsasha1

I think that for a 17 tire, 34 psi is what you should put. Not less. Driving with less air will ruin your tire really fast, breaking its side wall. (you'll see a crack line all around).

As for the bouncing, maybe one of your struts failed? but most likely that your plastic adapter inside the rim broke?

FlyRyde

I'll try swapping wheels, hows that? And if it still happens, I'll swap coilovers. I'll just knock down all the "could be"s.

DTN

Because the tire gets smaller so it does not throw off your speedometer. As the rim size increases, you get less sidewall or you end up with bigger wheels and a slower speedometer.



Hyundai recommends 30+ for a 15" rim. A 16 should be higher maybe 35PSI. They don't recomend 17s because there's not much rubber on the sidewalls. Seriously, go for 36-42psi for a 17" rim with low profile tires. Otherwise you're asking for trouble on potholes or speedbumps. A low profile tire WILL be a rough ride.

I run 40 psi in my 17"s

majik

I run 35-40 in my 17's.. they suggest 42.

The size of the tire also depends on how "flat" his 25-30psi was. That's pretty low, but not flat.

Have you checked yor tires? Running low PSI for so long (or even letting it sit still with low tire pressure) can cause the side walls to wear down, cause bubbles in the rubber, and wear unevenly. Check the tires for abnormal wear, bubbles in the rubber, uneven tread (of course it's uneven, you're lowered with 17's) but something that looks like it could be causing the "bumpy" feeling.

The same scenario would happen to me in the Mustang when the tires were too low. I had a slow leak in one tire, and when the PSI would drop to 25ish it would start to pull very hard on the interstate. That's how I knew it was time to fill it up again.

Or just swap out the rims and see if it fixes the problem. If the rim is bent, you might have to take the tire off before you could notice.

DTN

Yeah, and a bent rim dosn't have to be noticably bent. It can be uniformly warped or out-of-round. It happened to my stock 15"s from speedbumps and my last set of 17"s when I tried to keep 32PSI in them because I didn't know any better... Yeah, and you thought I bought my new rims because I'm made of money...

rallyman

Who is they? That is very dangerous to be running pressure that high, in my opinion. I hope the 42 psi you refer to is not the number you see on the sidewall of the tire. If it is, that is the maximum pressure that should be in the tire not the pressure you should run them at. I have had many different wheel and tire packages on numerous vehicles purchased from several different tire shops. Not one of them has ever suggested that a 17" tire should be run at 40 psi. They always say the manufacturers recommendation can still be followed.

I generally choose to set my tires at about 32 psi because I prefer them a little firmer for better handling. Air pressure is air pressure. A 15" tire that has 32 psi in it is no different than a 17" tire with 32 psi. Tire pressure should be checked and set when the tires are cold. If you set your tires to 40 psi they could easily be 45+ psi after driving a short distance and the tires have heated up. Over-inflating your low profile tires may give you slightly better protection from pothole damage to your wheel but it's not worth it to me. You might as well be driving around on solid rubber.

Blacktibs, I do agree with the others that you could be dealing with a bent wheel, suspension problems or even a tire problem. Let us know what you find out.

supercow

^^ditto




guys! that really high!

from: scc


blacktibs
I put ~34 in mine. And check about every month. Usually drops to 30-32 and I fill it back to 34. 25 is low yes. But not enough to make what he describes happen without something else being wrong. When was the last time you had a spin balance? You could have simply lost a weight.

KustomizedTiburon

i'm having the exact same problem in my neon and I know exactley what it is. One tire I ran flat for awhile and it actually broke a belt in the sidewall and another tire has a bubble in it. I just had them balanced and it didnt do a thing. I'd check over your tires, theres probably some sort of defect in them. up to 65 my car rides perfect, after that it rides horrible starts shaking and wobbling. I'm just glad it's the neon not the tib

majik

Honestly, I could be wrong. It's been probably over a year since I messed with the 17" tires (don't drive it). I'm most likely thinking of the Mustang's 15" tires. Regardless, I run about 5psi under the # marked on the sidewall.

If I'm checking or adding air, I always do it after driving on the interstate, never when they're cold. I agree that PSI is PSI, but having 25psi on 255/60/15 presents a different level of concern than 25psi on 205/40/17 IMO.


Edit:
Am I reading something wrong?
http://www.tirerack.com/tires/Spec.jsp?mak...ehawk+Wide+Oval

215/40/17 Firestone Firehawk Wide Ovals on my 17x7.5 Racing Harts:

205/40/17 84W XL
Treadwear: 320
Traction: AA
Temp: A
Max Load: 1102lbs. per tire
Max Inflation Press.: 50 psi
tread depth: 10/32"
Tire Weight: 21 pounds
Rim Width: 7-8"
Meas. Rim Width: 7.5"
Sect. Width: 8.5"
Tread Width: 7"
Overall Diam: 23.5"
Revs Per Mile: 886